Conventional epoxidation processes typically use silver-based catalysts for producing ethylene oxide (EO) from ethylene employing dioxygen as oxidant. The temperature and pressure for the conventional process are approximately 200° C. and 30 bars, respectively. Under these conditions, 10 to 15% of the ethylene in the conventional process is burned to carbon dioxide, rather than ethylene oxide, causing approximately $1 billion loss (based on global ethylene oxide production).
In the conventional process, the high temperatures employed result in the burning of the feedstock ethylene and product EO. To minimize this burning, a high ethylene gas hourly space velocity is maintained resulting in a per-pass ethylene conversion of 8%. At this low conversion, the selectivity towards EO is reported to be in the 85-90% range. Additional energy-intensive steps are required to separate and recycle the large amounts of unreacted ethylene from the product. Furthermore, the gaseous mixture of ethylene and EO is highly flammable in the presence of oxygen gas, which necessitates elaborate safety precautions in the design of the EO process equipment. Thus, there remains a need for an improved ethylene epoxidation process.